# SSLSetPeerDomainName(_:_:_:) Specifies the fully qualified domain name of the peer. ``` func SSLSetPeerDomainName(_ context: SSLContext, _ peerName: UnsafePointer?, _ peerNameLen: Int) -> OSStatus ``` ## Parameters `context` An SSL session context reference. `peerName` The fully qualified domain name of the peer—for example, `store.apple.com`. The name is in the form of a C string, except that `NULL` termination is optional. `peerNameLen` The number of bytes passed in the `peerName` parameter. ## Return Value A result code. See [Secure Transport Result Codes](/documentation/Security/secure-transport-result-codes). ## Discussion You can use this function to verify the common name field in the peer’s certificate. If you call this function and the common name in the certificate does not match the value you specify in the `peerName` parameter, then handshake fails and returns `errSSLXCertChainInvalid`. Use of this function is optional. This function can be called only when no session is active. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)